Graphics Reference
In-Depth Information
Figure 4.6.
Two-point perspective
view.
Figure 4.7.
Three-point perspective
view.
Three-point Perspective View.
Here we have three vanishing points and is the case
where none of the edges of the cube are parallel to the view plane. See Figure 4.7 and
the vanishing points
P
1
,
P
2
, and
P
3
.
Two-point perspective views are the ones most commonly used in mechanical
drawings. They show the three dimensionality of an object best. Three-point per-
spective views do not add much.
4.4
Windows and Viewports Revisited
The simple view of windows and viewports described in Chapter 1 glossed over some
important points and so we need to take another look. Assume that [wxmin,wxmax]
¥ [wymin,wymax] and [vxmin,vxmax] ¥ [vymin,vymax] define the window and view-
port rectangles, respectively. See Figure 4.8. We shall not change the basic idea that
a window specifies
what
we see and that the viewport specifies
where
we see it, but
there was a natural implication that it is by
changing
the window that one sees dif-
ferent parts of the world. Is that not how one would scan a plane by moving a rec-
